NAME

DESCRIPTION

This document describes differences between the 5.13.5 release and the 5.13.6 release.

If you are upgrading from an earlier release such as 5.13.4, first read perl5135delta, which describes differences between 5.13.4 and 5.13.5.

Core Enhancements

(?^...) regex construct added to signify default modifiers

A caret (also called a "circumflex accent") "^" immediately following a "(?" in a regular expression now means that the subexpression is to not inherit the surrounding modifiers such as /i, but to revert to the Perl defaults. Any modifiers following the caret override the defaults.

The stringification of regular expressions now uses this notation. E.g., before, qr/hlagh/i would be stringified as (?i-xsm:hlagh), but now it's stringified as (?^i:hlagh).

The main purpose of this is to allow tests that rely on the stringification to not have to change when new modifiers are added. See "Extended Patterns" in perlre.

"d", "l", and "u" regex modifiers added

These modifiers are currently only available within a (?...) construct.

The "l" modifier says to compile the regular expression as if it were in the scope of use locale, even if it is not.

The "u" modifier says to compile the regular expression as if it were in the scope of a use feature "unicode_strings" pragma.

The "d" modifier is used to override any use locale and use feature "unicode_strings" pragmas that are in effect at the time of compiling the regular expression.

use feature "unicode_strings" now applies to some regex matching

Another chunk of the "The "Unicode Bug"" in perlunicode is fixed in this release. Now, regular expressions compiled within the scope of the "unicode_strings" feature will match the same whether or not the target string is encoded in utf8, with regard to \s, \w, \b, and their complements. Work is underway to add the [[:posix:]] character classes and case sensitive matching to the control of this feature, but was not complete in time for this dot release.

\N{...} now handles Unicode named character sequences

Unicode has a number of named character sequences, in which particular sequences of code points are given names. \N{...} now recognizes these. See charnames.

New function charnames::string_vianame()

This function is a run-time version of \N{...}, returning the string of characters whose Unicode name is its parameter. It can handle Unicode named character sequences, whereas the pre-existing charnames::vianame() cannot, as the latter returns a single code point. See charnames.

Reentrant regular expression engine

It is now safe to use regular expressions within (?{...}) and (??{...}) code blocks inside regular expressions.

These block are still experimental, however, and still have problems with lexical (my) variables, lexical pragmata and abnormal exiting.

Custom per-subroutine check hooks

XS code in an extension module can now annotate a subroutine (whether implemented in XS or in Perl) so that nominated XS code will be called at compile time (specifically as part of op checking) to change the op tree of that subroutine. The compile-time check function (supplied by the extension module) can implement argument processing that can't be expressed as a prototype, generate customised compile-time warnings, perform constant folding for a pure function, inline a subroutine consisting of sufficiently simple ops, replace the whole call with a custom op, and so on. This was previously all possible by hooking the entersub op checker, but the new mechanism makes it easy to tie the hook to a specific subroutine. See "cv_set_call_checker" in perlapi.

To help in writing custom check hooks, several subtasks within standard entersub op checking have been separated out and exposed in the API.

Return value of delete $+{...}

Custom regular expression engines can now determine the return value of delete on an entry of %+ or %-.

keys, values work on arrays

You can now use the keys, values, each builtin functions on arrays (previously you could only use them on hashes). See perlfunc for details. This is actually a change introduced in perl 5.12.0, but it was missed from that release's perldelta.

Incompatible Changes

Stringification of regexes has changed

Default regular expression modifiers are now notated by using (?^...). Code relying on the old stringification will fail. The purpose of this is so that when new modifiers are added, such code will not have to change (after this one time), as the stringification will automatically incorporate the new modifiers.

Code that needs to work properly with both old- and new-style regexes can avoid the whole issue by using (for Perls since 5.9.5):

where $re_ref is a reference to a compiled regular expression. Upon return, $mods will be a string containing all the non-default modifiers used when the regular expression was compiled, and $pattern the actual pattern.

If the actual stringification is important, or older Perls need to be supported, you can use something like the following:

Regular expressions retain their localeness when interpolated

Regular expressions compiled under "use locale" now retain this when interpolated into a new regular expression compiled outside a "use locale", and vice-versa.

Previously, a regular expression interpolated into another one inherited the localeness of the surrounding one, losing whatever state it originally had. This is considered a bug fix, but may trip up code that has come to rely on the incorrect behavior.

Directory handles not copied to threads

On systems that do not have a fchdir function, newly-created threads no longer inherit directory handles from their parent threads. Such programs would probably have crashed anyway [perl #75154].

Negation treats strings differently from before

The unary negation operator - now treats strings that look like numbers as numbers [perl #57706].

Negative zero

Negative zero (-0.0), when converted to a string, now becomes "0" on all platforms. It used to become "-0" on some, but "0" on others.

If you still need to determine whether a zero is negative, use sprintf("%g", $zero) =~ /^-/ or the Data::Float module on CPAN.

Performance Enhancements

The bulk of the Tie::Hash::NamedCapture module used to be in the perl core. It has now been moved to an XS module, to reduce the overhead for programs that do not use %+ or %-.

Eliminate PL_* accessor functions under ithreads.

When MULTIPLICITY was first developed, and interpreter state moved into an interpreter struct, thread and interpreter local PL_* variables were defined as macros that called accessor functions, returning the address of the value, outside of the perl core. The intent was to allow members within the interpreter struct to change size without breaking binary compatibility, so that bug fixes could be merged to a maintenance branch that necessitated such a size change.

However, some non-core code defines PERL_CORE, sometimes intentionally to bypass this mechanism for speed reasons, sometimes for other reasons but with the inadvertent side effect of bypassing this mechanism. As some of this code is widespread in production use, the result is that the core can't change the size of members of the interpreter struct, as it will break such modules compiled against a previous release on that maintenance branch. The upshot is that this mechanism is redundant, and well-behaved code is penalised by it. Hence it can and should be removed.

Modules and Pragmata

Updated Modules and Pragmata

Archive::Extract has been upgraded from version 0.42 to 0.44

Carp has been upgraded from version 1.18 to 1.19.

It no longer autovivifies the *CORE::GLOBAL::caller glob, something it started doing in 1.18, which was released with perl 5.13.4 [perl #78082]

Compress::Raw::Bzip2 has been upgraded from version 2.030 to 2.031

Updated to use bzip2 1.0.6

CPAN has been upgraded from version 1.94_57 to 1.94_61

Data::Dumper has been upgraded from version 2.128 to 2.129.

Dumpxs no longer crashes with globs returned by *$io_ref[perl #72332].

Digest::MD5 has been upgraded from version 2.40 to 2.51.

It is now safe to use this module in combination with threads.

File::DosGlob has been upgraded from version 1.02 to 1.03.

It allows patterns containing literal parentheses (they no longer need to be escaped). On Windows, it no longer adds an extra ./ to the file names returned when the pattern is a relative glob with a drive specification, like c:*.pl[perl #71712].

File::Find has been upgraded from version 1.17 to 1.18.

It improves handling of backslashes on Windows, so that paths such as c:\dir\/file are no longer generated [perl #71710].

if has been upgraded from version 0.05 to 0.06

IPC::Cmd has been upgraded from version 0.60 to 0.64

IPC::Open3 has been upgraded from version 1.06 to 1.07.

The internal xclose routine now knows how to handle file descriptors, as documented, so duplicating STDIN in a child process using its file descriptor now works [perl #76474].

Locale::Codes has been upgraded from version 3.13 to 3.14.

Locale::Maketext has been upgraded from version 1.15 to 1.16.

It fixes an infinite loop in Locale::Maketext::Guts::_compile() when working with tainted values (CPAN RT #40727).

->maketext calls will now backup and restore $@ so that error messages are not suppressed (CPAN RT #34182).

Math::BigInt has been upgraded from version 1.95 to 1.97.

This prevents sqrt($int) from crashing under use bigrat;[perl #73534].

NEXT has been upgraded from version 0.64 to 0.65.

overload has been upgraded from version 1.10 to 1.11.

overload::Method can now handle subroutines that are themselves blessed into overloaded classes [perl #71998].

PathTools has been upgraded from version 3.31_01 to 3.34.

podlators has been upgraded from version 2.3.1 to 2.4.0

sigtrap has been upgraded from version 1.04 to 1.05.

It no longer tries to modify read-only arguments when generating a backtrace [perl #72340].

Internal Changes

The sv_cmp_flags, sv_cmp_locale_flags, sv_eq_flags and sv_collxfrm_flags functions have been added. These are like their non-_flags counterparts, but allow one to specify whether get-magic is processed.

The sv_cmp, sv_cmp_locale, sv_eq and sv_collxfrm functions have been replaced with wrappers around the new functions.

A new sv_2bool_flags function has been added.

This is like sv_2bool, but it lets the calling code decide whether get-magic is handled. sv_2bool is now a macro that calls the new function.

A new macro, SvTRUE_nomg, has been added.

This is like SvTRUE, except that it does not process magic. It uses the new sv_2bool_flags function.

sv_catsv_flags no longer calls mg_get on its second argument (the source string) if the flags passed to it do not include SV_GMAGIC. So it now matches the documentation.

The LINKLIST macro, part of op building that constructs the execution-order op chain, has been added to the API.

Many functions ending with pvn now have equivalent pv/pvs/sv versions.

The save_freeop, save_op, save_pushi32ptr and save_pushptrptr functions have been added to the API.

The new API function parse_stmtseq() parses a sequence of statements, up to closing brace or EOF.

Selected Bug Fixes

A regular expression match in the right-hand side of a global substitution (s///g) that is in the same scope will no longer cause match variables to have the wrong values on subsequent iterations. This can happen when an array or hash subscript is interpolated in the right-hand side, as in s|(.)|@a{ print($1), /./ }|g[perl #19078].

Parsing Perl code (either with string eval or by loading modules) from within a UNITCHECK block no longer causes the interpreter to crash [perl #70614].

When -d is used on the shebang (#!) line, the debugger now has access to the lines of the main program. In the past, this sometimes worked and sometimes did not, depending on what order things happened to be arranged in memory [perl #71806].

The y/// or tr/// operator now calls get-magic (e.g., the FETCH method of a tie) on its left-hand side just once, not twice [perl #76814].

This bug was introduced in an earlier 5.13 release, and does not affect perl 5.12.

When a tied (or other magic) variable is used as, or in, a regular expression, it no longer has its FETCH method called twice [perl #76814].

This bug was introduced in an earlier 5.13 release, and does not affect perl 5.12.

The -C command line option can now be followed by other options [perl #72434].

Assigning a glob to a PVLV used to convert it to a plain string. Now it works correctly, and a PVLV can hold a glob. This would happen when a nonexistent hash or array element was passed to a subroutine:

Stringifying a scalar containing -0.0 no longer has the affect of turning false into true [perl #45133].

Aliasing packages by assigning to globs or deleting packages by deleting their containing stash elements used to have erratic effects on method resolution, because the internal 'isa' caches were not reset. This has been fixed.

sort with a custom sort routine could crash if too many nested subroutine calls occurred from within the sort routine [perl #77930].

This bug was introduced in an earlier 5.13 release, and did not affect perl 5.12.

The eval_sv and eval_pv C functions now set $@ correctly when there is a syntax error and no G_KEEPERR flag, and never set it if the G_KEEPERR flag is present [perl #3719].

The XS multicall API no longer causes subroutines to lose reference counts if called via the multicall interface from within those very subroutines. This affects modules like List::Util. Calling one of its functions with an active subroutine as the first argument could cause a crash [perl #78070].

Many of the changes included in this version originated in the CPAN modules included in Perl's core. We're grateful to the entire CPAN community for helping Perl to flourish.

Reporting Bugs

If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/perlbug/ . There may also be information at http://www.perl.org/ , the Perl Home Page.

If you believe you have an unreported bug, please run the perlbug program included with your release. Be sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of perl -V, will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.

SEE ALSO

The Changes file for an explanation of how to view exhaustive details on what changed.